Most integrated circuit (IC) manufacturing processes typically include a number of manufacturing steps that can sequentially form, shape or otherwise modify various layers. One way of forming a layer can be to deposit and then etch the layer. Usually, etching can include forming an etch mask over an underlying layer. An etch mask may have a particular pattern that can mask certain portions of an underlying layer while exposing other portions. Etching can then remove portions of an underlying layer exposed by an etch mask. In this way, an etch mask pattern may be transfect to an underlying layer.
Etching may include “wet” chemical etching and “dry” plasma etching. In many cases, plasma etching can provide greater controllability and greater directional control (e.g., anisotropy) if desired.
An important issue in conventional plasma etching processes can be the redistribution of etched material. This issue will be explained with reference to FIG. 4. FIG. 4 is a side cross sectional view of various chamber parts 400 in a plasma reactor chamber that may hold a wafer 402.
In an etch process, active species of a plasma can etch materials on a wafer 402 surface and redistributed such materials onto chamber parts 400. If redistributed material is allowed to accumulate, such accumulated material can detach from chamber parts 400 and then land on a wafer, possibly forming a defect. Consequently, periodic maintenance of plasma etching equipment often includes cleaning chamber parts 400 to remove material redistributed by a reactive plasma.
As noted above, conventional etching in an integrated circuit manufacturing process can include an etch mask. Etch masks are often formed from photoresist. Photoresist typically includes a polymer-based material with an activating agent. When exposed to particular electromagnetic wavelengths (e.g, visible light X-rays, etc.) an activating agent may form crosslinks between polymers. A solvent can then be applied to a photoresist. Those portions of photoresist having crosslikes are less soluble than those portions of photoresist not having crosslinks. Thus, portions of photoresist exposed by a photomask can be remove. In this way, photolithographic techniques may then be used to “develop” and then form a pattern in photoresist with a photomask, or the like.
The transfer of a photoresist pattern to an underlying layer by etching typically relies on a high degree of selectivity between an etch mask layer and an underlying layer. However, while a plasma etch may have a such high degree of selectivity, active species within a plasma may still etch portions of an etch mask and redistribute etch mask material onto chamber parts.
Thus, periodic maintenance procedures are typically performed on etch systems to remove photoresist polymers that have been redistributed on etch chamber equipment.
A conventional plasma chamber part cleaning process will now be described with reference to FIG. 5. A conventional chamber part cleaning process 500 may include an initial wet chemical cleaning (step 502). For example, chamber equipment may be submerged in a mixture of hydrogen peroxide (H2O2) and ammonium hydroxide (NH24OH). More particularly, chamber equipment may be submerged in a 30% solution of H2O2 in a 1:1 ratio with NH4OH for about 20 minutes.
Following a step 502, chamber parts may be rinsed in de-ionized (DI) water (step 504). Pressurized nitrogen gas (N2) under may then be used to blow dry chamber parts after being rinsed (step 506).
A method 500 may continue with an oven bake (step 508). An oven bake may particularly include loading blown dry chamber parts into an oven and baking the chamber parts for 30 minutes at about 110° C.
A drawback to a conventional method 500 can be how such a cleaning method affects chamber part surfaces. For example, chamber parts can typically be formed from quartz. A wet clean of H2O2 and NH4OH may each quartz surfaces changing surface textures. Changes in chamber part surfaces may result in drift in an etch process, as a changing surface conditions may alter gas flows and or etch chemistry. Further, because cleaning may consume etch chamber parts, such parts may have to be periodically replaced.
A conventional method 500 may include other drawbacks. First it has been observed that such a cleaning process may result in particles remaining on chamber parts. Thus, there may be an initial increase in particle defects following periodic maintenance of a plasma etching system. In addition, following a conventional cleaning process such as that shown in FIG. 5, redistributed polymer material may not adhere as well to etch chamber part surfaces. Consequently, such etch chamber parts may have to be cleaned with a certain minimum frequency to prevent redistributed material from accumulating to a point where it can contaminate wafers.
It would be desirable to arrive at some way of cleaning reactive plasma chamber parts that may address the various drawbacks of conventional cleaning processes.